This application claims priority from Japanese Applications 11-018137, filed on Jan. 27, 1999 and 12-004304, filed on Jan. 13, 2000, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a method for evaluation of abrasion of a forming mold, a production system for molded parts, and a forming mold for mass production, and more particularly, the invention relates to a method for evaluation of abrasion of a resin forming mold, a production system for resin molded parts, and a resin forming mold for mass productions
2. Description of the Related Art
In the forming mold for mass production of molded parts, injection molding for molded parts has been carried out by scores of thousands to hundreds of thousands of shots per unit. In the forming mold for mass production of this kind, the shots are repeated many times whereby the surface of the mold piece constituting a cavity for forming molded parts is worn by ejecting a forming raw material into the cavity. The cavity termed herein is a portion into which raw material is charged in the forming mold, and is a hollow place formed by a fixed mold and a movable mold.
In the case of a molded part having a complicated construction, the shape of the cavity is complicated corresponding to the shape of the molded part. Therefore, the surface of the mold piece or the surface portion thereof having a high resistance of a flowing molten raw material into the cavity is worn greatly. For example, where resin containing glass fiber or the like is used as the raw material, a degree of abrasion is very large.
When the surface of the mold piece becomes worn, an error occurs in dimension of a molded part produced thereby. To prevent this, in designing a mold, the number of shots of the molded parts that can be produced by the forming mold for mass production is planned and limited in advance.
In such a case as described, if the entire mold piece of the forming mold for mass production is abandoned after shotting of the planned number of the molded parts, it results in the waste of still usable part of the forming mold for mass production, therefore, the cost of the forming mold for mass production is highly reflected so that the cost of the molded parts increases.
In view of the foregoing, it is desired that abrasion of the mold piece is evaluated in advance. If a degree of abrasion of the surface of the mold piece can be grasped easily in advance, the result of the evaluation of abrasion can be utilized for the design of the mold piece of the forming mold for mass production, which is therefore desirable.
The subject of this invention is to provide a method for evaluation of abrasion of a forming mold, a production system for molded parts, and a forming mold for mass production, which enables the evaluation of a degree of abrasion of the surface of the mold piece easily and while avoiding an increase in cost.
For solving the above-described subject, according to a first aspect of this invention, there is provided a method for evaluation of abrasion of a forming mold, including a dividing step for dividing a mold piece into a plurality of divided pieces, where the mold piece constitutes a cavity for forming a molded part, and a judging step for judging an abrasion amount of a surface of each of the plurality of divided pieces, where the abrasion results from charging raw material into a cavity.
Thereby, the mold piece is divided into a plurality of pieces and the abrasion amount can be judged in unit of each divided piece. Therefore, there can be obtained an effect capable of easily grasping a progressing degree of abrasion of which part of the surface of the mold piece is large.
According to a second aspect of this invention, there is provided a method for evaluation of abrasion of the forming mold, wherein the abrasion amount of the surface of each of the plurality of the divided pieces is judged in a state where each of the divided pieces is removed from the forming mold body.
Thereby, there can be obtained an effect of measuring the abrasion amount of the removed divided pieces by a simple measuring instrument such as slide calipers, a micrometer and easily judging a progressing degree of abrasion.
According to a third aspect of this invention, there is provided a method for evaluation of abrasion of the forming mold, wherein the abrasion amount of the surface of each of the plurality of the divided pieces is judged in a state where each of said divided pieces is not removed from a forming mold body.
Thereby, since the abrasion amount can be judged without removing the divided pieces, there can be obtained an effect capable of achieving higher efficiency in terms of time and labor of the abrasion evaluation process. Further, there can be also obtained an effect of being free from occurrence of a mounting error in remounting because there is no steps of removing and remounting.
According to a fourth aspect of this invention, there is provided a method for evaluation of abrasion of the forming mold, wherein a layer having a predetermined thickness is formed on the surface of each of the divided pieces, and when the layer is disappeared, it is judged that the abrasion amount in excess of the predetermined thickness is present.
According to a fifth aspect of this invention, there is provided a method for evaluation of abrasion of the forming mold, including a forming step for forming a multi-layer composed of a plurality of layers having a predetermined thickness, respectively, and different colors on the surface of each of the divided pieces, and a judging step for judging the abrasion amount of the surface of each of the divided pieces from a change in color resulting from peeling of the respective layers of the multi-layer.
According to a sixth aspect of this invention, there is provided a method for evaluation of abrasion of the forming mold, wherein a first marking-off line having a predetermined depth is formed on the surface of each of the divided pieces, and when the first marking-off line is disappeared, it is judged that the abrasion amount in excess of the predetermined depth is present.
According to a seventh aspect of this invention, there is provided a method for evaluation of abrasion of the forming mold, wherein a second marking-off line having a deeper marking-off depth than the predetermined depth of the first marking-off line is formed on the surface of each of the divided pieces.
According to an eighth aspect of this invention, there is provided a method for evaluation of abrasion of the forming mold, wherein satin having a predetermined depth of rugged portions is formed on the surface of each of the divided pieces, and when the satin is disappeared it is judged that the abrasion in excess of the predetermined depth be present.
According to the fourth to eighth aspects of this invention, since the degree of abrasion of the surface can be grasped easily and quantitatively by viewing the surface of the mold piece, there can be obtained an effect capable of achieving higher efficiency in terms of time and labor of the abrasion evaluation process than in the third aspect.
Further, since in the seventh aspect, two kinds of marking-off lines different in depth are formed, there can be obtained an effect capable of judging the abrasion amount of higher accuracy from the state of disappearance of the marking-off line.
According to a ninth aspect of this invention, there is provided a method for evaluation of abrasion of a forming mold, including an examining step for examining dimensions of individual portions of a molded part to be formed from raw material charged into a cavity, and an evaluating step for evaluating thereby an abrasion amount of a surface of the mold piece for forming the molded part, the surface corresponding to a portion of each of the molded part.
Thereby, there can be obtained an effect capable of indirectly evaluating the degree of abrasion of the surface of the mold piece without removing the mold from the molding machine or removing the mold piece from the molding machine, and without forming the marking-off line or the layer on the mold piece.
According to a tenth aspect of this invention, there is provided a method for evaluation of abrasion of a forming mold, wherein the mold pieces of a forming mold for mass production are divided in accordance with the abrasion amount of divided pieces.
Thereby, there can be obtained an effect capable of planning a way of dividing the mold piece of the forming mold for mass production, materials for the mold piece, and the like on the basis of a quantitative, a qualitative or indirect degree of abrasion evaluation.
According to an eleventh aspect of this invention, there is provided a production system, including a preparing step for preparing a forming mold for test having a mold piece constituting a cavity for forming a molded part and evaluating an abrasion amount of a surface of the mold piece, the abrasion resulting from charging raw material into the cavity, evaluating step for evaluating the abrasion amount of the surface of the mold piece by carrying out a test shot by the forming mold for test, a fabricating step for fabricating a forming mold for mass production on the basis of a result of evaluation of the abrasion amount, and a molding step for molding the molded part using the forming mold for mass production.
According to a twelfth aspect of this invention, there is provided the production system, wherein the forming mold for mass production has a mold piece divided into a plurality of divided pieces on the basis of evaluation of the abrasion amount by the test shot, and the mold piece further constitutes a cavity for forming a molded part.
According to a thirteenth aspect of this invention, there is provided a production system, wherein replacing period for divided pieces is determined on the basis of the abrasion amount.
According to a fourteenth aspect of this invention, there is provided a production system, wherein replacing period is determined on the basis of the number of shot times.
According to a fifteenth aspect of this invention, there is provided a production system, wherein replacing period is determined on the basis of integrating time from a start of use of the forming mold for mass production.
According to a sixteenth aspect of this invention, there is provided a production system further including a disassembling step for disassembling the forming mold for mass production into divided pieces, a cleaning step for cleaning the surface of each divided piece by removing each of the divided pieces, a measuring step for measuring the abrasion amount of the surface of each divided piece, a sorting step for sorting the divided piece judged to be replaced on the basis of the result of measurement and a divided piece judged to be continuously usable, replacing step for replacing the divided piece judged to be replaced on the basis of the result of measurement with a new divided piece, and a reassembling step for reassembling the divided piece judged to be continuously usable and the new divided piece replaced on the forming mold for mass production.
According to a seventeenth aspect of this invention, there is provided a production system including an observing step for observing the abrasion state of the surface of each of the divided pieces without removing the divided pieces to visually conform the abrasion amount, and a removing step for removing only the divided piece judged to be replaced on the basis of the result of the visual confirmation from the forming mold for mass production to replace the divided piece judged to be replaced with a new divided piece.
According to the eleventh to seventeenth aspects, there can be obtained an effect that the process planning from the design of the forming mold for mass production to repairs thereof can be done systematically.
According to an eighteenth aspect of this invention, there is provided a forming mold for mass production, including divided pieces divided into a plurality of pieces according to an abrasion amount of a surface, the abrasion resulting from charging raw material into a cavity for forming a molded part.
Thereby, the replacement of only the greatly worn divided piece suffices, and accordingly, there can be obtained an effect that the service life of the mold for mass production can be extended, and the cost of the molded part can be reduced.
According to a nineteenth aspect of this invention, there is provided a forming mold for mass production, wherein replacing period for the divided pieces is determined on the basis of the abrasion amount.
Thereby, the greatly worn divided piece suffices to be removed every predetermined shot and replaced with other divided pieces remained mounted, thus obtaining an effect capable of saving trouble of replacing mold pieces.
According to a twentieth aspect of this invention, there is provided a forming mold for mass production, wherein the divided pieces are formed of materials different in hardness.
Thereby, a high-hardness material can be used for divided pieces, which are large in degree of abrasion to uniformly adjust a degree of abrasion of divided pieces, thus obtaining an effect capable of replacing the divided pieces at once. Further, a low hardness and inexpensive material can be selected for divided pieces, which are small in degree of abrasion, thus obtaining an effect of achieving the reduction in cost.